1. Field of the Invention
The invention relates to a frequency converter for an immersion vibrator.
2. Description of the Related Art
Immersion vibrators are used for compressing concrete while it is still liquid. To do this, a vibrator bottle which is part of the immersion vibrator is immersed in the concrete, and an electric motor and an imbalance, which is driven by this electric motor at a high rotation speed, are accommodated in this vibration bottle. In order to achieve the required motor rotation speed and hence compression frequency, the motor must be supplied with a special voltage, whose frequency (for example, 200 Hz) is greater than the mains frequency provided by the public mains system.
It is known for the special voltage to be provided by a special voltage network or by a frequency converter, which is either provided on site in the form of a large stationary unit, or is an integrated component of the immersion vibrator. An immersion vibrator with an integrated frequency converter is known from DE G 92 17 854.5.
CH 689598 A5, describes an immersion vibrator in which a converter can be disconnected from a protective sleeve which is fitted with a vibration bottle. The protective sleeve is coupled to the converter via a specially designed electromechanical plug and socket structure, so that not only is it possible to transfer the special voltage, but this also ensures a mechanically firm connection between the protective sleeve and the converter housing. The specific configuration of the electromechanical coupling means that the elements to be coupled must be accurately matched to one another. It is impossible to use components which are not equipped for the specific coupling.
Immersion vibrators with an integrated frequency converter have proven to be excellent in practice. However, as before, immersion vibrators which do not have their own frequency converter and must be fed by an external frequency converter are still used on building sites. These immersion vibrators are primarily distinguished by their cheaper procurement costs. However, on building sites, they require either an appropriate special voltage network at a low voltage level and a high voltage frequency, or a conventional frequency converter, which must be provided where the work is being carried out in the form of a very heavy box. This makes it very difficult to operate such an immersion vibrator.
Objects and Summary of the Invention
The invention is based on the object of specifying a frequency converter which also makes it possible for immersion vibrators without their own integrated frequency converters to utilize the advantages of immersion vibrators with their own frequency converter, when desired.
The object is achieved, by a frequency converter as in accordance with the present invention.
A frequency converter according to the invention has a mobile converter housing with a converter circuit, and is characterized in that a plug socket is provided which is fed with the special voltage from the converter circuit and into which a plug part of the immersion vibrator can be inserted. According to the invention, it is thus possible to plug the mains plug, which is used as the plug part, of an immersion vibrator which does not have its own frequency converter into the plug socket of the frequency converter, with the plug socket being integrated in the converter housing, or being capable of being connected to the converter housing via a further supply cable. It is thus possible, without incurring any particular additional costs and without having to accept any particular physical complexity, to convert an immersion vibrator without its own frequency converter to an immersion vibrator with a frequency converter.
One advantageous embodiment of the invention is characterized in that the plug socket can be fed with the mains voltage as an alternative to the special voltage, and in that a changeover switch is provided for switching between the special voltage and the mains voltage. The immersion vibrator can thus—as before—also be connected to a special voltage network without the frequency converter having to be removed from it. This has the advantage that the frequency converter cannot be lost during the busy operations on a building site. In a further advantageous embodiment of the invention a securing device is provided in the region of the plug socket, by means of which the plug part of the immersion vibrator is held in the plug socket. The securing device is thus used for strain relief and allows the operator to pull the frequency converter behind him on the immersion vibrator. For this purpose, the converter housing advantageously has an elongated external shape with minimized transverse dimensions, which makes it considerably easier for the converter housing to slide on the building site, which generally has numerous pieces of reinforcing ironwork. The mobile handling of the frequency converter is additionally improved by the converter housing having a smooth outer skin.